The present invention relates to a gas flow type angular velocity sensor which is capable of sensing a deflection of gas flow in a gas path of a sensor body by a pair of heat wires when an angular velocity acts on the sensor's body.
Recently, as known from Japanese laid open patent publication No. 29858/91, a gas flow type angular velocity sensor has been developed, wherein a body portion including a gas path and a pair of heat wires arranged in the gas path is manufactured by semiconductor micromachining on the basis of IC technology.
In this type angular velocity sensor, as shown in FIGS. 7, 8 and 9, the body portion is constructed in such a way that a lower semiconductor substrate 1 having an etched thereon half groove 41 and an upper semiconductor substrate 2 having an etched thereon half groove 41 are bonded to each other so as to precisely couple the half grooves 41 to form a gas path 4 in the assembled body portion.
The lower semiconductor substrate 1 has an etched therein bridge portion 6 whereon a pair of heat wires 51 and 52 are formed by patterning.
Each of the lower and upper semiconductor substrates 1 and 2 also has an etched half-hole 31 forming a nozzle hole 3 when both substrates are coupled with each other. The lower semiconductor substrate 1 has electrode portions 7 formed by patterning at both sides of paired heat wires 51 and 52.
The problem faced in the manufacture of the above-mentioned conventional device is that many micromachining operations are required for forming a half-groove 41 on each of the lower and the upper semiconductor substrates 1 and 2 and much labour is further required for precisely coupling with each other the half-grooves 41 on both substrates to form gas path 4 therein.
Another problem is that the manufacturing process involves the possibility of damaging the paired heat wires when the bridge portion 6 is formed by etching a part of the lower semiconductor substrate underneath the paired heat wires previously formed by depositing material such as platinum on the lower semiconductor substrate 1.